柴油污染含水层的自然衰减作用

Natural attenuation of diesel in aquifers

柴油污染对人类健康和生态环境具有很大危害。自然衰减以其经济、易操作、对人危害小和降解污染物彻底等优点,成为国内外比较常用的水土污染修复方式之一。采用室内实验的方式,以柴油作为修复对象,模拟了含水层系统中柴油污染物随地下水迁移转化的过程,以自然衰减作为修复方式,研究其修复机理。通过分析计算总石油烃（TPH）污染晕的变化规律,计算修复时间和截留率等方法,研究了柴油污染含水层中的自然衰减强度及修复效能。结果显示,柴油进入含水层后,逐渐形成了稳定的污染晕,并在地下水流场中沿各个方向不断迁移并衰减,其迁移速率由快变慢,并趋于稳定,且沿流向上的迁移作用最强,垂向上次之;＂断源＂后,含水层中的TPH浓度随时间呈明显的下降趋势,自然衰减作用变得明显;结合一阶反应动力学方程,计算出下部含水层的修复时间为1.0～1.5a,表层注油点位置地下水的修复时间约为2.6a;含水层对柴油具有截留作用,截留作用初期较为稳定,近饱和后作用渐弱,停止注油后,截留作用重新渐变明显;自然衰减可作为修复地下水柴油污染的有效方式。

Diesel pollution is harmful to health and environment. Natural attenuation becomes a more common soil remediation way at home and abroad,because it is economic,easy to operate,less harmful to human and has a complete degradation of pollutants. Diesel is used as the repair object and indoor experiment is conducted. The migration and transformation process of diesel pollutants in the aquifers with groundwater flow are simulated and the repair mechanisms by using natural attenuation is examined. The intensity and recovery performance of natural attenuation in the diesel-contaminated aquifer is investigated through analyzing the TPH plume variation and calculating repair time and retention rate. The results show that a stable pollutant plume in the aquifer was gradually formed. The plume migrated along every direction and attenuated. The migration rate changed from fast to slow,then the plume tended to be stable. The migration along the flow direction was the strongest,and vertical direction was followed. After the diesel source was cut off,the concentrations of TPH in the aquifer significantly decreased with time,and natural attenuation became apparent. According to the firstorder kinetic equation,the repair time of the lower aquifer was calculated as 1. 0 to 1. 5 a,and the repair time of the surface groundwater was about 2. 6 a. The aquifer had an interception fanction to diesel. The interception was stable at the beginning,and gradually weakened when the aquifer was nearly saturated. After the diesel source was cut off,the interception become significantly re-graded. Natural attenuation could be an effective method to repair diesel contaminated groundwater.